class A:

    def __init__(self, a, b):
        self.a = int(a)
        self.b = int(b)

    def add(self):
        return self.a + self.b


class B(A):

    def sub(self, a, b):
        return a - b


a = A('3', 2)
b = B(2, 3)
print(a.add())
print(b.add())
print(b.sub(4, 3))

try:
    print(c)
except Exception as msg:
    print(msg)
finally:
    print("finally")
